1. Field of the Invention
The present invention relates to a curve sensor to detect the curved state of a curving measurement target.
Background Art
2. Description of the Related Art
A curve sensor to detect the curved state (curving angle or curving direction) of a curving measurement target is generally known. For example, such a curve sensor guides light having a predetermined optical characteristic emitted from a light source to an optical fiber provided with a curved state detecting unit. At this time, the light amount in the curved state detecting unit changes in accordance with the curving angle and curving direction of the optical fiber. Based on the change in the light amount, the curved state of the optical fiber, thereby the curved state of the curving measurement target is detected.
As an example of such a curve sensor, Jpn. Pat. Appln. KOKAI Publication No. 2007-44412 has disclosed an endoscope insertion shape detection probe to detect the shape of an insertion tube of an endoscope. The probe comprises a probe body, and a module connected to the probe body. The outer diameter of the probe body is formed to be less than the inner diameter of a forceps channel in the endoscope. The probe body comprises a light supply fiber, curvature detection fibers provided with light loss portions, and a mirror disposed at the distal ends of the light supply fiber and the curvature detection fibers.
When the insertion shape of the endoscope is detected, the probe body is first inserted into the forceps channel in the endoscope. Light emitted from a light source is then guided by the light supply fiber and reflected by the mirror at the distal end. The reflected light is then guided by the curvature detection fibers, and received on a module side from the proximal end of the curvature detection fibers. The amount of the light guided by the curvature detection fibers has changed by the leakage of the light in the light loss portions, and the curving angle or curving direction of the curvature detection fibers at the light loss portions is detected on the basis of the amount of the light received on the module side. In this way, the insertion shape of the endoscope in which the probe body is inserted is detected.